A random walk model of ovum transport

This paper discusses the random nature of ovum transport, and presents a Brownian Motion model of ovum transport in the ampulla and isthmus. A new explanation of the delay in transport at the ampullary-isthmic junction, based on widely differing diffusion coefficients for the ampulla and isthmus, is proposed.     

The cytosol receptors for progesterone in the different parts of rabbit fallopian tube and uterus during ovum transport

Progesterone receptors were determined in the cytosol from the ampulla, ampullaryisthmic junction and isthmus of rabbit fallopian tube and uterus of estrus and pregnant rabbits. The receptor levels when compared among its various anatomical segments, were the same in ampulla, isthums and uterus but maximum in ampullary-isthmic junction. Significant differences were observed in mated animals at 14, 24, 34, 48, 70 and 144 h after coitus. The receptor concentrations in portions of the fallopian tube showed no significant change between 14 and 24 h after coitus, except for a decrease in ampullary-isthmic junction at 24 h. At 34 h the concentration of receptor further decreased in all parts of the tube. At 48 and 70 h after coitus, receptor concentrations decreased gradually in ampulla and ampullary-isthmic junction, while isthmus showed a gradual increase. At 144 h, the receptor concentration showed no further change in ampulla and ampullary-isthmic junction; however, isthmus showed a decline. The uterine receptor concentration declined steadily from estrus till 70 h after coitus, however, it was increased at 144 h. The dissociation constant (K_d) of cytosol receptor in all the tissues at estrus and during early pregnancy was found similar. The implications of these changes in relation to the normal ovum transport have been correlated in this paper.     

Variations in rabbit oviduct microvascular architecture after ovulation induced by hCG

Rabbits were induced to ovulate by injection with hCG and vascular corrosion casts of the oviducts were examined by scanning electron microscopy after 24 and 48 h, when the ova would be expected to be at the ampullary-isthmic junction, and traversing the isthmus respectively. At 24 h there was dilatation of the isthmic subserosal venous plexus. It is suggested that venous distension in the isthmic subserosal venous plexus, due to raised venous pressure or to reduced venous wall tone, may occlude the isthmic lumen to ova, and thus explain the known pre-isthmic delay in ovum transport. By 48 h after hCG, distension was no longer evident, consistent with the possibility of ovum transport.     

Spontaneous motility of the oviduct in the anaesthetized pig

Intraluminal pressure microtransducers were placed at the uterotubal junction, the proximal isthmus, the ampullary-isthmic junction and the mid-ampulla. Spontaneous motility occurred throughout the oestrous cycle in all segments. During oestrus there were regular, high amplitude peristaltic waves in all segments, superimposed on basal activity. On Day 1 of the cycle the pattern was mostly antiperistaltic, presumably related to sperm transport. During the periovulatory period the number of peristaltic and antiperistaltic waves became equal, perhaps in relation to the transport of gametes to the fertilization site. During Day 3 there was no peristaltic activity; the motility patterns of the isthmus and ampullary-isthmic junction were similar (regular phasic contractions of high frequency and amplitude) while the ampullary motility was low. On Day 4, when the eggs enter the uterine lumen, the ampullary-isthmic junction and particularly the isthmus showed strong contraction waves (mostly peristaltic) superimposed on the basal phasic activity. This suggests an active role of the smooth muscle of the lower oviducal segments in ovum descent. During the mid- and late-luteal phases, the isthmus remained motile, with an irregular base line, but lost the pattern of basal contractions that dominated the activity during the first 4 days of the cycle. The ampulla showed low levels of spontaneous motility throughout the rest of the cycle.     

Studies on the ultrastructure of the Fallopian tube: Part II. Changes in the secretory cells of the rabbit Fallopian tube during ovum transport

The ultrastructural changes that occur in the ciliated cells of the tubal epithelium of the adult rabbit during ovum transport were previously reported. In this communication, the changes that occur in the secretory cells of the tube under identical conditions are described. Estrous and pregnant rabbits were used. 14-70 hours postcoitum the size and shape of the microvilli of the ampullar cells differed from the isthmic ones. The prominence of the microvilli was roughly correlated with the possible arrival of the ovum in any part of the tube. The secretory granules in the cells of the ampulla were more electron dense than those in the isthmus. With the progress of the post ovulatory period, the secretory granules changed in nature and location. During the postovulatory period, the secretory process in both parts of the tube indicate a "merocrine" type of secretion. A cilium was occasionally present in the luminal epithelium of a secretory cell. Hybrid cells may arise when a cell malfunctions while receiving a set of messages from the nucleus at the time appropriate for cell differentiation.     

Ultrastructural changes in the oviductal epithelium of Merino ewes during the estrous cycle

Isthmic and ampullary oviductal epithelia sampled from Merino ewes at days -1, 1, 3, and 10 of the estrous cycle (estrus = day 0) were studied by scanning and transmission electron microscopy after fixation by vascular perfusion. Secretory cells, ciliated cells, and lymphocytelike basal cells were observed in both isthmic and ampullary epithelium at all stages of the estrous cycle studied and their ultrastructural features were analyzed. Synthesis of lamellated secretory granules occurred in the ampullary secretory cells during the follicular and early luteal phases, and their contents were released by exocytosis into the oviductal lumen during the luteal phase. Granule release was associated with nucleated apical protrusion of these cells into the oviductal lumen. No such secretory activity was displayed by isthmic secretory cells even though a few cells contained nonlamellated granules. Apocrine release of apical vesicles and accompanying cytoplasmic material from apical protrusions of ciliated cells occurred in the isthmus around estrus but not in the ampulla. This unexpected feature has not previously been reported in any other mammal. Dendritic basal cells were distinguished in the lower part of the epithelium by their heterochromatic nuclei, electron-lucent cytoplasm, and lack of attachment zones. No migration of basal cells was observed, and their ultrastructural features were similar in the ampulla and isthmus and at all stages of the estrous cycle examined. The function of these lymphocytelike cells in the epithelium is uncertain, but the presence of phagocytic bodies and lysosomes in 20% of them may indicate a phagocytic role.     

Glycogen distribution in porcine fallopian tube epithelium during the estrus cycle

Histochemical features of two different parts of the porcine Fallopian tube have been studied, with special reference to cyclic changes in the distribution of glycogen particles. Porcine Fallopian tubes were obtained from a local slaughterhouse. Slides were studied under light microscopy utilising histological and histochemical techniques. The most striking feature during the periovulatory stage of the estrus cycle was the occurrence of glycogen granules in the apical cytoplasm of epithelial cells in both the ampulla and isthmus of the Fallopian tubes. In the isthmus, cells containing numerous granules of polysaccharides aggregated into areas of different sizes were noted after ovulation. During the midluteal phase their number was minimal or were even absent. In the ampula typical extrusion of secretory granules and nuclei protruding into the tubal lumen was visible after ovulation. In the luteal phase a lot of nuclei protruded into the tubal lumen and some free in the lumen were noted. It is possible that glycogen in the preovulatory stage functions as a source of energy for ciliary movement and as a nourishment for the ovum. In the isthmus large number of aggregated glycogen particles was observed also after ovulation. In this stage of the cycle, numerous granules of polysaccharide aggregated in isthmus epithelium could be the major energy source for embriogenesis when the embryo travels down the Fallopian tubes, during the early cleavage stage.     

Histochemical and radioautographic study of glycoprotein secretion in the epithelium lining the uterine tubes of mice

Summary Two-month-old female Swiss mice that had come into estrus were injected intravenously with L-³H-fucose and killed at 5, 15, 40 min, and 4 h after injection. Pieces of the isthmus and of the ampulla of the uterine tubes were processed for light-and electron-microscopic radioautography. Incorporation of ³H-fucose was more intense in the isthmian secretory cells than in the ciliated cells of the ampulla. Electron-microscopic radioautography of the isthmian secretory cells demonstrated that ³H-fucose was incorporated into newly synthesized glycoproteins in the Golgi apparatus from where labelled glycoproteins migrated mainly to secretory granules and apical microvilli. The histochemical technique using ruthenium red confirmed the presence of glycoproteins in the contents of the secretory granules released to the lumen of the uterine tubes as demonstrated by radioautography. Other glycoproteins are transported inside small vesicles and most likely are related to the renewal of the plasma membrane. The role of the secretory glycoproteins in various events of mammalian reproduction is discussed.     

Nuclear estrogen and progesterone receptors in the oviduct of heifers under natural and superovulated estrous cycles

Oviducts from 22 crossbred heifers were examined for the presence of nuclear estrogen (ERalpha) and progesterone (PR) receptors at different phases (estrus, metaestrus and diestrus) of naturally occurring estrous cycles and estrous cycles during which superovulation was induced. Receptors were detected by immunohistochemistry in the epithelial cells, connective tissue and muscular layer of oviductal infundibulum, ampulla, ampullary/isthmic transition and isthmus. Epithelial ERalpha was found along the entire oviduct regardless of the cycle phase and of the circulating concentrations of 17beta-estradiol (E(2)) and progesterone (P(4)). Epithelial PR was found mainly at the ampullary-isthmic transition and isthmus and more intensely at the estrus phase but their amount was not correlated with P(4) concentrations. ERalpha in the connective tissue was more abundant at the infundibulum and ampulla, regardless of the phase of the estrous cycle and of E(2) and P(4) circulating concentrations. PR in the connective tissue was found mostly at the ampulla, regardless of the estrous cycle phase but no correlations were found between amount and P(4) concentrations. ERalpha staining intensity in the muscular layer was similar at all phases of the estrous cycle and at all anatomical segments of the oviducts. However, PR staining was more intense at the isthmus during the metaestrus phase and it was negatively correlated with P(4) concentrations. In general, data from the present research suggest that P(4) exerts an inhibitory role upon ERalpha and PR. Also, no differences were found between animals subjected or not to superovulation.     

Ultrastructure of mucous cells from the oviduct epithelium of the rabbit (Lepus cuniculus). Preliminary study]

Authors studied the ultrastructural features of the mucous cells present in the three segments of the rabbit oviduct in anoestrous. Results showed that only one kind of mucous cell was present in the isthmus while two different kinds of mucous cells were found in the ampulla and infundibulum. The ultrastructural features observed in the isthmic cells correlated well with the histochemical data already described in that segment. However such correlations could not be made between the ampulla and infundibulum. Authors suggest that the ampulla can be considered a transitional segment between isthmus and infundibulum.     

Effects of delayed transfer and treatment with oestrogen on the transport of microspheres by the rat oviduct

Starch or dextran blue microspheres were transferred microsurgically to the infundibulum of the oviduct on Days 1, 2, or 3 of pregnancy of control and oestradiol-treated rats. The animals were killed a few hours to several days after transfer to assess the number and distribution of ova and microspheres in the tract. After transfer on Day 1 of pregnancy, microspheres and eggs crossed the ampullary-isthmic junction (AIJ) 18 h after ovulation. After transfer on Day 2 of pregnancy, more than 50% of microspheres were retained in the ampulla, indicating that the AIJ changes again 34 h after ovulation. Treatment with oestradiol did not advance the passage of eggs or microspheres across the AIJ but caused accelerated transport through the isthmus as soon as the eggs or microspheres reached this segment. Dextran blue microspheres were seen to move back and forth in the isthmus of control anaesthetized rats at a frequency of 5-6 times/min. Between 7 and 20 h after treatment with oestradiol the frequency of these movements was significantly augmented, indicating that increased frequency of contractions of the smooth muscle of the isthmus precedes and accompanies accelerated transport of ova through this segment.     

Synthesis and secretion of sulphated glycoproteins by rabbit oviduct explants in vitro

The ability of rabbit oviduct explants to incorporate radiolabelled precursors into specific secretory products was investigated. Ampullary and isthmic oviduct segments were cultured in the presence of [3H]glucosamine or [35S]sodium sulphate. Medium samples were analysed for the presence of secreted, labelled macromolecules. Explants incorporated the [3H]glucosamine and secreted labelled glycoproteins in vitro. SDS gel electrophoresis and subsequent fluorographic analysis of culture medium demonstrated a differential secretion of glycoproteins between the ampulla and the isthmus. Although ampullary tissue secreted a greater amount of labelled glycoproteins during the sampling period, the major secretory constituent of Mr approximately 66,000 was common to both oviduct segments. Tissue incubated with [35S]sodium sulphate also secreted a labelled glycoprotein or subunit of Mr approximately 66,000. The results indicate that rabbit oviduct explants are capable of synthesis and secretion of specific sulphated glycoproteins in vitro and that there is a difference in the type and amount of secretion produced between the two oviduct segments.     

Attachment of boar sperm to mucosal explants of oviduct in vitro: possible role in formation of a sperm reservoir

Ejaculated boar sperm were incubated with explants of porcine oviductal mucosa that had been dissected from the isthmic and ampullar regions of gilts. Sperm bound within minutes to the epithelial surfaces of the explants. Binding was not affected by region (isthmus or ampulla) nor day of estrous cycle (Day 0 or Day 10), but was increased by addition of 70 pg/ml 17 beta-estradiol to the medium. Scanning electron micrographs indicated that sperm bound, via the acrosomal region, to ciliated cells. After 24 h, the numbers of bound sperm dropped significantly, but the motility of the bound sperm did not. A mucous material that entrapped sperm was observed on the epithelial surfaces of 23/32 isthmic and only 4/32 ampullar explants. These results indicate that sperm sticking to ciliated cells and mucus can create a sperm reservoir in the isthmus, but the means by which sperm are released remain unknown.     

Morphometric and ultrastructural features of the mare oviduct epithelium during oestrus

Morphometric, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations have displayed regional differences in the mare oviductal epithelium. The entire mucosa of the oviduct was lined with a pseudostratified epithelium, which consisted of two distinct cell types, ciliated and non-ciliated. Ciliated cells were predominant in the three different segments of the oviduct and their percentage increased from fimbriae to ampulla and significantly decreased in the isthmus. SEM revealed in the infundibulum finger-like mucosal folds, some of them interconnected, in the ampulla numerous and elaborated branched folds of the mucosa, whereas the isthmus displayed a narrow lumen, short and non-branched mucosal folds. In the ampulla and isthmus the majority of non-ciliated cells showed apical blebs provided or not of short microvilli. TEM displayed different ultrastructural features of ciliated and non-ciliated cells along the oviduct. Isthmus ciliated cells presented a more electron-dense cytoplasm than in infundibulum and ampulla cells and its cilia were enclosed in an amorphous matrix. The non-ciliated cells of infundibulum did not contain secretory granules but some apical endocytic vesicles and microvilli coated by a well developed glycocalyx. Non-ciliated cells of ampulla and isthmus contained secretory granules. Apical protrusions of ampulla displayed two types of secretory granules as well as occasional electron-lucent vesicles. Isthmus non-ciliated cells showed either electron-lucent or electron-dense cytoplasm and not all contained apical protrusions. The electron-dense non-ciliated cells displayed microvilli coated with a well developed glycocalyx. Three types of granules were observed in the isthmus non-ciliated cells. The regional differences observed along the epithelium lining the mare oviduct suggest that the epithelium of the each segment is involved in the production of a distinctive microenvironment with a unique biochemical milieu related to its functional role.     

Attachment and release of spermatozoa from the caudal isthmus of the hamster oviduct

Female hamsters were mated shortly after the onset of oestrus. At 3 or 6 h after mating, the right oviduct was flushed in situ with 30, 90 or 180 microliters medium to remove spermatozoa from the lumen, leaving only those firmly attached to the isthmic mucosa of the oviduct. When eggs were recovered from oviducts at 20 h after flushing the majority were fertilized, indicating that the spermatozoa that were firmly attached to the mucosa were capable of detaching and ascending to the ampulla to fertilize eggs. Neither the time of flushing nor the volume of flushing medium had a significant effect on the percentage of spermatozoa that remained in the isthmus after flushing. These results suggest that there is no change in the surface of the oviduct mucosa that causes the release of spermatozoa from the caudal isthmus near the time of ovulation. When incapacitated spermatozoa were introduced into the oviduct, many of them attached to oviductal mucosa, while capacitated spermatozoa did not. This indicates that it is a change in the sperm surface, rather than the mucosal surface, that causes the release of spermatozoa, i.e. spermatozoa remain attached to the isthmic mucosa until they become capacitated and then detach and migrate to the ampulla to fertilize the eggs.     

Effect of ovulation and sperm motility on the migration of rabbit spermatozoa to the site of fertilization.

Few spermatozoa were present in the ampullae of females 12 h after intravaginal artificial insemination (AI) when there was no ovulation-inducing stimulus. When ovulation was induced, sperm distributions in the female tract 12 h after AI did not differ from those observed 12 h after natural mating. The number of spermatozoa in the oviductal isthmus was similar in all 3 groups as was the percentage of isthmic spermatozoa exhibiting 'activated' motility. When fertile mating was delayed for 8 or 12 h after coitus with a vasectomized male (i.e. 2 h before or after ovulation), spermatozoa were not present in the ampulla 4 h later. The numbers of spermatozoa recovered from the cranial isthmus after delayed matings and 12 h after natural matings did not differ, but after delayed matings the motility of isthmic spermatozoa was non-progressive or poorly progressive and none exhibited 'activated' motility. Flagellar activity of isthmic spermatozoa recovered 4 h after delayed matings and after natural matings was similarly depressed. These observations indicate that sperm ascent to the tubal ampulla in the sustained phase of transport, though enhanced by ovulation, must also depend on changes in flagellar activity and a specific pattern of motility, both of which appear only after spermatozoa have resided for more than 4 h in the female tract.     

The polyol pathway in the bovine oviduct

The oviducts likely provide optimized micro‐environments for the final maturation of gametes, fertilization, and early embryo development. Hexoses, including glucose, fructose, and sorbitol, are involved in these critical reproductive events. Monosaccharide production is controlled, in part, by the polyol pathway and requires two enzymes: an aldose reductase (AR) that reduces glucose into sorbitol, followed by its oxidation into fructose by sorbitol dehydrogenase (SDH). We analyzed the expression of AR and SDH in the isthmus and ampulla of the bovine oviduct at the proliferative, mid‐luteal, and late‐luteal phases of the estrous cycle by quantitative PCR and immunoblots. Immunochemistry and an assay of SDH activity were also performed. The quantity of hexoses in whole sections of isthmus and ampulla were determined by liquid chromatography coupled to mass spectrometry. In sum, AR expression was restricted to the isthmus, while SDH was mostly expressed in the isthmic–ampullary junction and the ampulla, specifically concentrated in the luminal epithelium of the oviduct. The estrous cycle had no impact on protein expression of AR and SDH. Instead, the levels of AR and SDH expression were associated with higher ratios of sorbitol to fructose in the isthmus (1.6) than in the ampulla (4.1; P = 0.005). These results are discussed in light of physiological events occurring in the oviduct. Mol. Reprod. Dev. 79: 603–612, 2012. © 2012 Wiley Periodicals, Inc.     

Unexpected flagellar movement patterns and epithelial binding behavior of mouse sperm in the oviduct

In order to better understand how sperm movement is regulated in the oviduct, we mated wild-type female mice with Acr-EGFP males that produce sperm with fluorescent acrosomes. The fluorescence improved our ability to detect sperm within the oviduct. Oviducts were removed shortly before or after ovulation and placed in chambers on a warm microscope stage for video recording. Hyperactivated sperm in the isthmic reservoir detached frequently from the epithelium and then reattached. Unexpectedly, most sperm found in the ampulla remained bound to epithelium throughout the observation period of several minutes. In both regions, most sperm produced deep flagellar bends in the direction opposite the hook of the sperm head. This was unexpected, because mouse sperm incubated under capacitating conditions in vitro primarily hyperactivate by producing deep flagellar bends in the same direction as the hook of the head. In vitro, sperm that are treated with thimerosal to release Ca(2+) from internal stores produce deep anti-hook bends; however, physical factors such as viscous oviduct fluid could also have influenced bending in oviductal sperm. Some sperm detached from epithelium in both the ampulla and isthmus during strong contractions of the oviduct. Blockage of oviduct contractions with nicardipine, however, did not stop sperm from forming a storage reservoir in the isthmus or prevent sperm from reaching the ampulla. These observations indicate that sperm continue to bind to oviductal epithelium after they leave the isthmic reservoir and that sperm motility is crucial in the transport of sperm to the fertilization site.     

Electromyographic activity and noradrenaline content of the rabbit oviduct under different hormonal states

Spontaneous electromyographic (EMG) activity of the oviduct recorded in vivo in untreated, estrogen-treated, and progesterone-treated castrated rabbits was found to exhibit two main patterns: short spike bursts lasting 1-10 s and long trains of action potentials lasting several minutes, which constituted the major component of EMG activity. After estrogen treatment, both wet weight and noradrenaline (NA) content of the castrated rabbit oviduct were enhanced mainly at the ampullary-isthmic junction; long trains of discharges were significantly shorter (2.0-2.7 min vs 3.6-4.6 min) and appeared at more frequent intervals (9.8-12.2 min vs 14.2-22.6 min). After progesterone treatment, spontaneous EMG activity was not significantly different from that in untreated castrated rabbits (as was the NA content) except at the ampullary-isthmic junction. NA injection elicited a stimulatory response of the oviduct lasting 1-7 min in the three hormonal states. Phentolamine strongly depressed spontaneous EMG activity but the inhibition was more transient in castrated rabbits than in estrogen-treated and progesterone-treated animals. Propranolol had no effect on spontaneous EMG activity. These data and the high NA concentrations found in all parts of the isthmus support the hypothesis that adrenergic innervation plays a role in the organization of oviductal motility in the rabbit.     

Concentrations of energy substrates in oviductal fluid and blood plasma of pigs during the peri-ovulatory period.

Large White gilts, 9 to 18 months old, that had exhibited at least two natural oestrous cycles were divided into three groups (phases): unmated pre-ovulatory, unmated post-ovulatory and mated post-ovulatory (n = 16, 20 and 18). Oviductal luminal fluid samples were collected under anaesthesia by micropipette from the ampulla and ampullary-isthmic junction and analysed by an ultramicrofluorometric technique. Glucose concentrations (mmol 1(-1), means combining regions; mean +/- SEM) were significantly higher in blood plasma than in oviductal fluid (4.56 +/- 0.20 versus 0.59 +/- 0.16; P < 0.0001; n = 27), whereas lactate was higher in the oviduct (5.71 +/- 0.53 versus 2.48 +/- 0.24; P < 0.0001; n = 27). No significant differences were found between the ampulla and the ampullary-isthmic junction. However, the concentration of glucose was significantly higher (P < 0.05) in the ampulla of the pre-ovulatory group (0.97 +/- 0.20; n = 13) compared with the mated group (0.25 +/- 0.05; n = 14) and its concentration in the ampullary-isthmic junction in the pre-ovulatory group (1.65 +/- 0.63; n = 13) was significantly greater (P < 0.05) than in the post-ovulatory (0.43 +/- 0.11; n = 11) or mated groups (0.17 +/- 0.02; n = 14). Lactate in the ampulla of mated animals was higher than in the pre-ovulatory group (6.83 +/- 0.70 versus 3.86 +/- 0.38; P < 0.05; n = 15 and 13), but neither was significantly different from the post-ovulatory group. Furthermore, no change was seen at the ampullary-isthmic junction in lactate concentration with phase.(ABSTRACT TRUNCATED AT 250 WORDS)